1. Field of the Invention
The present invention relates to novel pyrimidinedione derivatives and acid addition salts thereof, to methods of preparing the same and to pharmaceutical agents containing the same, which are effective for the treatment of cardiac dysfunctions such as arrhythmia and cardiac insufficiency.
2. Description of the Related Art
The mechanism of the occurrence of arrhythmia is complicated. Abnormalities in stimulation production and disorders in the conducting system or combinations thereof are considered to be responsible.
As to disorders in excitation conduction, the reentry theory is representative.
One of the conditions of occurrence of arrhythmia is irregularity in the refractory period in various parts of the heart. In addition, one-directional block, shortened refractory period, delay in conduction and the presence of circus movement are complicatedly involved.
Heretofore, various antiarrhythmic agents have been used for the treatment of arrhythmia.
The antiarrhythmic agents are classified into four groups according to their modes of action.
That is, E. M. Vaughan Williams (Vaughan Williams E. M.; "Advances in drug research, Vol 9", ed. by Harper N. J., Simmonds A. B., Academic Press, London, 1974, pages 69-101) have classified the antiarrhythmic agents into the following four groups in accordance with their actions against the action potential of cardiac muscle or against the ionic current which generates the action potential.